AbstractTunable polymer Bragg grating filters with extremely high tuning efficiency are demonstrated. A buried heating scheme is used to achieve fairly uniform heating conditions in the polymer waveguide. Thermal simulation results indicate that the temperature change per unit heating power at the core of the waveguide can be significantly increased by implementing sufficient thermal buffers around it. Simulated and experimental results are in very good agreement. Tuning efficiency has been improved to a record 425 nm/W, corresponding to a tuning power of 88 mW for a wavelength tuning range of close to 40 nm.